public class Test6 {
    public static void main(String[] args) {
        StringBuilder sb=new StringBuilder();
        System.out.println(sb);
        sb.append(1);
        sb.append("aaa");
        sb.append(true);
        System.out.println(sb);
        sb.reverse();
        System.out.println(sb);
        int length=sb.length();
        System.out.println(length);

    }
}
